Condensate stripper



Oct. 20,1953 v. LARSEN 2,656,262

CONDENSATE STRIPPER Filed March 28, 1951 Z 7ZZ/e7?%n l e J Q7 1567;

?atented Oct. 20, 19 53 UNITED i=3.

OFFICE CONDENSATE STBIPPER Lyle V. Larsen, Chicago, Ill., assignor to Chicago Bridge & Iron Company, a corporation of Illinois 9 Claims.

This invention relates to lifter roof tanks for the storage of volatile liquids and more particularly to apparatus for removing and returning product condensate from the water seal provided between the tank shell and roof of a lifter roof tank by utilizing the difference in specific gravity of the water and the condensate.

Volatile liquids, such as gasoline and other petroleum products, may be stored in tanks provided with a roof which may rise and fall with expansion and contraction of the vapors within the tank. Such tanks of course must be provided with sealing means between the roof and the upper part of the tank shell. One such means comprises a water sealing trough adapted to cooperate with a skirt on the roof which dips into the water in the trough to seal the space between the roof and tank shell. The skirt must be made sufiiciently deep and the trough surficiently deep to insure that the skirt is immersed in the water in all positions of the roof relative to the shell. As condensate from the tank contents collected on the surface of the sealing water inside the skirt, additional depth of trough and additional depth of skirt was necessary to prevent the condensat from escaping to the outside of the tank when the roof was at its upper limit of travel.

The present invention provides a means whereby the condensate collecting upon the surface of the water may be returned to the tank contents automatically with the movements of the roof relative to the shell. The apparatus thus enables the tank to be constructed with a substantial savings in metal both in the trough and the skirt. Any combination of sealing liquid and condensate may be used with the invention so long as the condensate will float on the sealing liquid and be immiscible therewith.

The invention will be described in connection with one embodiment thereof illustrated in the accompanying drawings, in which:

Fig. 1 is a fragmentary vertical section through one wall of a lifter roof tank showing the invention therein and the roof in its upper extreme position relative to the tank shell; Fig. 2 is like Fig. 1 showing the roof in a position slightly lowered from the position of the roof illustrated in Fig. 1; and Fig. 3 is a view similar to Figs. 1 and 2 showing the roof in its lowermost position relative to the tank shell.

As illustrated in the drawings, the lifter roof tank has a shell within which the contents such as gasoline or other volatile products may be stored. A strengthening annular girder H is provided about the upper portion of the shell l0 adjacent the upper free edge thereof. A roof l2 having a slight conical pitch is provided with a depending skirt I5 about its periphery, For the sake of clarity, roof trusses and bracing as well as guide structure for the roof have been omitted from the drawings. A sealing trough is provided about the upper portion of the shell and is formed with a bottom it secured to the shell it and an annular outer trough plate i! joined to the bottom plate It. A Wing girder I8 is provided about the upper part of the outer trough plate 11 to strengthen the structure. The space thus enclosed by the tank shell ill and the plates 16 and ll is nearly filled with water It. The level of the water is generally maintained close to the top or th outer trough plate II.

All the space within the lifter roof tank above the liquid level therein will be filled with vapors of the stored liquid. As the vapors strike the metal of the roof and the depending skirt [5, some condensation will occur which will result in a pool 20 of gasoline or the like floating on the sealing water [9. This condensate may be removed and returned to the tank contents by the apparatus of this invention.

A reservoir or chamber 2|, here shown as having a box-like cross section, may be secured to the lower portion of the skirt [5. The reservoir is provided with a plurality of openings 22 extending through the skirt l5 and communicating with the reservoir and the space inside the skirt. The reservoir 2| may be a pip or other member forming an elongated chamber which extends circumferentially of the skirt l5. A number of reservoirs may be provided if desired and each may be only a few feet in length. In areas where condensation of the contents of the tank occurs very rapidly, it may be desirable to extend the chamber 2| completely around the skirt [5 and to provide a number of openings 22 communicating with the chamber. The number and capaciti of the chambers or reservoirs will be dictated primarily by the rate of condensation occurring in the particular application and location.

In Fig. 1 it will be noted that the reservoir 2! is secured to the skirt at a position above the level of the sealing liquid when the roof is in its uppermost position. As the roof lowers, the opening 22 registers with the'pool of condensate 26 on the inside of the skirt and admits condensate into the reservoir. A riser pipe 25 is connected with the interior of the reservoir and extends upwardly therefrom to a discharge end 26 positioned Within the tank. The capacity of that it the riser pipe is small as compared with the capacity of the reservoir. Upon further movement of the roof from the position shown in Fig. 2 to the lowermost position shown in Fig. 3, the water [9 also enters the chamber or reservoir and because of the difference in specific gravities of the condensate and the water, forces the condensate out of the riser pipe 25 and back into the tank. It will be noted that the opening 22 is at the lower portion of the reservoir so that condensate may be trapped within the reservoir as the roof moves downwardly. g

The reservoirs 2| may be secured to the inner side of the skirt and the riser pipes also located inside the skirt if desired. When water or other the accumulation of a column of condensate on the sealing liquid inside the skirt.

While I have shown and described certain embodiments of my invention, it is to be understood is capable of many modifications.

Changes, therefore, in the construction and arrangeme-nt may be made without departing from the spirit and scope of. the invention as disclosed in the appended claims.

I claim:

1.. In a lifter roof tank having a trough adapted to contain a, sealing liquid heavier than and immiscible with the tank contents and having a skirt on the roof adapted to dip into the sealing liquid, 2. condensate stripper, comprising, a

reservoir secured to. the lower portion of the skirt and having communication with the portion of the sealing trough on the interior of the skirt and a riser pipe communicating at its lower end with said reservoir and at its upper end with the interior of the tank, the upper end of said pipe being above the Sealing trough in all, positions of the roof with respect tothe tank shell, whereby condensate on the surface of the sealing liquid inside said skirt may be returned to. the tank upon lowering. of the kirt and roof.

2. The condensate stripper as set forth in claim 1 in which, the reservoir is positioned on the skirt above they bottom thereof and in a position to be above the sealing liquid level. when the roof is in its upper extreme position relative to the tank shell.

3. The condensate stripper as set forth in claim 1 in which, the reservoir extends circumferentially of the skirt and is provided with a plurality of openings at the bottom edge of the reservoir for communication with said portion of the sealing trough to trap, condensate within the reservoir.

4. The condensate stripper as set forth in claim 1 in which, the capacity of the riser pipe is substantially. less than the capacity of said reservoir.

5. In a lifter roof. tank having a side wall, a

trough about the side wall adapted to hold a sealing liquid, a roof and a skirt on the roof adapted to extend into the sealing liquid, said skirt having a depth to extend below the outer level of the sealing liquid a distance equal to the maximum operating pressure of the tank in inches of water when the roof is in its uppermost position, a condensate stripper, comprising, a horizontally extending reservoir secured to the lower portion of the skirt and having a plurality of openings communicating with the portion of the sealing trough inside said skirt, said reservoir being positioned above the bottom of the skirt and being adapted to be carried into and out of the sealing liquid during movement of the roof between its extreme upper and lower positions, and. a riser pipe leading from the reservoir upwardly to its upper end in communication with the interior of the tank whereby condensate floating on the sealing liquid inside said skirt may be trapped in the reservoir and returned to the tank through said riser pipe.

6. The condensate stripper as set forth in claim 5 in which, the reservoir is secured to the outer side of the skirt with said openings extending through the skirit and said riser pipe extends upwardly from the reservoir and through the skirt near the roof.

7. The condensate stripper as set forth in claim 8 in which, the reservoir has a box-like cross-section and said openings communicate with the lower portion of the reservoir.

8. In a lifter roof tank having a tank shell, a water sealing trough about the tank shell, a roof and a skirt on the roof adapted to dip into the water sealing trough, said tank being adapted to contain a volatile liquid capable of floating on water, a condensate stripper, comprising, a reservoir secured to the lower portion of the skirt and having communication with the sealin trough inside the skirt, a riser pipe communicating at its respective ends with the reservoir and the interior of the tank and having a capacity substantially smaller than said reservoir whereby condensate on the surface of the water seal inside the skirt may be floated upwardly from the reservoir through the riser pipe and back into the tank upon downward movement of the skirt into the sealing liquid.

9. Apparatus for removing and elevating a floating liquid from the surface of a heavier liquid, comprising, hollow housing forming a chamber and having openings in its lower portion for admitting liquid into the chamber, a riser pipe having a lower end communicating with the upper portion. of said chamber and an upper discharge end, said chamber being adapted to receive and retain the floatin liquid therein with initial immersion thereof and to receive the heavier liquid upon further immersion, said riser pipe having a capacity substantially less than said chamber whereby the floating liquid may be raised through said riser pipe and discharged therefrom with continued lowering of the chamber into said heavier liquid.

LYLE' V. LARSEN.

No references cited. 

1. IN A LIFTER ROOF TANK HAVING ATROUGH ADAPTED TO CONTAIN A SEALING LIQUID HEAVIER THAN AND IMMISCIBLE WITH THE TANK CONTENTS AND HAVING A SKIRT ON THE ROOF ADAPTED TO DIP INTO THE SEALING LIQUID, A CONDENSATE STRIPPER, COMPRISING A RESERVOIR SECURED TO THE LOWER PORTION OF THE SKIRT AND HAVING COMMUNICATION WITH THE PORTION OF THE SEALING TROUGH ON THE INTERIOR OF THE SKIRT AND A RISER PIPE COMMUNCIATING AT ITS LOWER END WITH SAID RESERVOIR AND AT ITS UPPER END WITH THE INTERIOR OF THE TANK, THE UPPER END OF SAID PIPE BEING ABOVE THE SEALING TROUGH IN ALL POSITIONS OF THE ROOF WITH RESPECT TO THE TANK SHELL, WHEREBY CONDENSATE ON THE SURFACE OF THE SEALING LIQUID INSIDE SAID SKIRT MAY BE RETURNED TO THE TANK UPON LOWERING OF THE SKIRT AND ROOF. 